feat: add react-resizable-panels dependency and update canvas components for improved layout

- Introduced the react-resizable-panels package to enhance panel resizing capabilities.
- Refactored CanvasPage to utilize CanvasShell for a cleaner layout.
- Updated CanvasSidebar to support a compact mode and improved rendering logic for user entries.
- Enhanced CanvasUserMenu with a compact option for better UI adaptability.

package.json

@@ -36,6 +36,7 @@
     "radix-ui": "^1.4.3",
     "react": "19.2.4",
     "react-dom": "19.2.4",
+    "react-resizable-panels": "^4.8.0",
     "resend": "^4.8.0",
     "shadcn": "^4.1.0",
     "tailwind-merge": "^3.5.0",